feat: add token usage tracking, context display, and dynamic context length (#132)

* fix: specify TS_NODE_PROJECT for dev:server script

ts-node/register resolves tsconfig from the entry file upward,
finding the root solution-style tsconfig.json (no compilerOptions).
This causes target to default to ES3, breaking MapIterator spread
syntax (TS2802). Set TS_NODE_PROJECT env var to point to the server
tsconfig which targets ES2024.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add token usage tracking, context display, and dynamic context length

- Intercept SSE proxy to capture run.completed events and persist token
  usage (input_tokens, output_tokens) per session to SQLite/JSON store
- Display context usage bar in ChatInput showing used/total/remaining tokens
- Resolve actual context length from Hermes models_dev_cache.json based
  on the active profile's default model (fallback 200K), with 5min in-memory cache
- Move sessions-db.ts to db/hermes/ for unified database layer
- Add usage store with SQLite + JSON fallback (auto-migration via ensureTable)
- Fix proxy SSE path regex to match rewritten upstream path
- Fix route ordering: /sessions/usage before /sessions/:id to avoid 404
- Fetch per-session usage on session enter instead of batch
- Add unit tests for usage-store, db index, and proxy SSE interception

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/client/src/i18n/locales/de.ts

@@ -61,6 +61,7 @@ export default {
 
   // Chat
   chat: {
+    contextRemaining: 'übrig',
     emptyState: 'Starten Sie eine Konversation mit Hermes Agent',
     inputPlaceholder: 'Nachricht eingeben... (Enter zum Senden, Shift+Enter fur neue Zeile)',
     attachFiles: 'Dateien anhangen',